Mechanical aspects of ferro-elastic behavior and phase composition of La0.58Sr0.4Co0.2Fe0.8O3

Phase composition and thermo-mechanical properties of La0.58Sr0.4Co0.2Fe0.8O3-delta (LSCF) have been studied. The LSCF perovskite material comprised two phases: rhombohedral and cubic, with a ratio that showed to depend on both cooling rate as well as atmosphere. The fracture stress of LSCF was determined on the basis of ring-on-ring bending tests between room temperature (RT) and 800 degrees C. Below 700 degrees C nonlinear load-displacement curves were obtained, an effect that is attributed to the ferro-elasticity of the rhombohedral phase. Both SEM and TEM verify the existence of a domain structure in the rhombohedral grains. The indentation fracture toughness appears to be insensitive to temperature variations from RT up to 350 degrees C. The importance of thermal history on phase composition and the resulting thermo-mechanical behavior is discussed. (C) 2009 Elsevier B.V. All rights reserved